A wave of fierce bombardments reportedly hit the capital of Sudan after a ceasefire period specified by one of the warring factions came to an end on Monday morning.

Clashes between the Sudanese military and the paramilitary group Rapid Support Forces erupted on April 15. The World Health Organization said that more than 420 people have been killed.

The violence prompted governments, including that of Japan, to evacuate their nationals from Sudan.

After the RSF-set truce period ended on Monday morning, airstrikes hit the capital Khartoum, according to local media and journalists. Gunfire was reportedly heard as well.

The prospect of an escalation of violence is rising. A local medical group said in a social media post that a fierce bombardment was taking place in Khartoum and asked healthcare professionals for help in treating the injured at hospitals.

There are concerns that the humanitarian situation in the country will deteriorate. People are reported to be struggling with power outages and limited access to clean drinking water and food.

British broadcaster BBC reported that up to 20,000 people have fled Sudan to seek safety in Chad, and that roughly 10,000 refugees have arrived in South Sudan.

UN Secretary-General Antonio Guterres called on the warring parties to halt fighting immediately. He said during a speech at the UN Security Council on Monday that the fighting "risks a catastrophic conflagration within Sudan," which he said could engulf the entire region and beyond.